Joint Auto-Exposure Tone-Mapping for HDR to LDR Compression
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Solution Overview
Problem
Conventional techniques for compressing high bit-depth images into low bit-depth images fail to maintain clarity and contrast, especially in low visibility scenarios.
Innovation Solution
A method and system for tone-mapping that jointly execute auto-exposure and tone-mapping algorithms, using data from the auto-exposure system of a sensor to create high-quality low dynamic range (LDR) images from high dynamic range (HDR) images.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional compression techniques are used to convert HDR images to LDR images, then the bit-depth is reduced for display compatibility, but the clarity and contrast of the image are lost
Solution Approach 1:
The patent applies parameter changes by computing a virtual gain based on image statistics and using it to generate a tone-mapping function. The virtual gain adjusts the mapping parameters dynamically based on the input image characteristics, allowing the system to preserve clarity and contrast while converting from HDR to LDR format. This is evident in the claims where the tone-mapping function is generated based on the virtual gain and luminosity probability density function.
2Manufacturing precision
If high bit-depth is used to capture detailed images in low visibility scenarios, then image quality is improved, but the image size and processing complexity increase
Solution Approach 1:
The patent extracts only the essential information needed for quality LDR conversion by computing image statistics and a luminosity probability density function. Instead of processing all HDR image data, the system extracts key statistical parameters to generate the tone-mapping function, thereby reducing processing complexity while maintaining image quality. This is reflected in the method of computing virtual gain based on image statistics rather than processing the entire high-bit-depth image.
3Ease of manufacture
If separate auto-exposure and tone-mapping systems are used, then each function can be optimized independently, but the overall system complexity increases
Solution Approach 1:
The patent merges auto-exposure and tone-mapping into a unified system by computing the virtual gain based on image statistics that inform both auto-exposure decisions and tone-mapping function generation. The same image statistics and virtual gain parameter are used for both functions, eliminating the need for separate independent systems while maintaining the ability to optimize each function. This integration is evident in the joint computation approach described in the claims.
Data Source
AI summary
The present disclosure describes compression of high dynamic range (HDR) images into low dynamic range (LDR) images while saving useful data in the HDR image. HDR images can be formed by merging images with different exposure times into a single image with high bit-depth to capture low light and bright data. LDR images can be generated using a joint auto-exposure and tone mapping system to capture useful details of the HDR input in and LDR output. Therefore, embodiments of the present disclosure create high quality LDR images from HDR images using data from the auto-exposure system of a sensor.